Hubble, Gemini Spot ‘Hyperactive’ Stars in Small, Young Galaxies

We all know youngsters are a handful, but this really takes the cake: astronomers have clocked the speeds of stars in infant galaxies at about a million miles an hour, about twice the pace of our Sun’s cruise through the Milky Way.

The small galaxies date to 11 billion years ago, when the universe was just a couple billion years old. Their stars, astronomers say, are buzzing and whirling at head-spinning rates.

Researchers spotted the galaxies with NASA’s Hubble Space Telescope and the 8-meter Gemini South telescope in Chile. Hubble revealed that the galaxies are a fraction the size of most galaxies we see today, and Gemini clocked their speed by using spectroscopy.

The Gemini near-infrared spectroscopic observations required an extensive 29 hours on the sky to collect the extremely faint light from the distant galaxy, which goes by the designation 1255-0.

The results will be published in the August 6, 2009 issue of the journal Nature, with a companion paper in the Astrophysical Journal.

“This galaxy is very small, but the stars are whizzing around as if they were in a giant galaxy that we would find closer to us and not so far back in time,” says Pieter van Dokkum, professor of astronomy and physics at Yale University in New Haven, Connecticut, who led the study.

The researchers say it is difficult to explain how such compact, massive galaxies form, and why they are not seen in the current, local universe. “One possibility is that we are looking at what will eventually be the dense central region of a very large galaxy,” explains team member Marijn Franx of Leiden University in the Netherlands. “The centers of big galaxies may have formed first, presumably together with the giant black holes that we know exist in today’s large galaxies that we see nearby.”

The most massive galaxies we see in the local universe (where we don’t look back in time significantly) that have a mass similar to 1255-0 are typically five times larger than the young compact galaxy. How galaxies grew so much in the past 10 billion years is an active area of research, and understanding the dynamics in these young compact galaxies is a key piece of evidence in eventually solving this puzzle.

To witness the formation of these extreme galaxies, the astronomers plan to observe galaxies even farther back in time with Hubble’s new Wide Field Camera.

Source: Early press release out of the Space Telescope Science Institute (StSci). For illustrations and more information, visit the Hubble Site or the Gemini Observatory online. The ApJ paper doesn’t appear to be published online yet, but check back for the link!